Images for Final Approval:

{what follows is the original post}
Lisa -- Here is a rough prototype of a Basset for a cake topper. I started with the assumptions that
1) the cake topper shouldn't be larger than 5 inches in diameter; so the green base that I built here is 5" across. The basset is a bout 5 inches long, 1 1/2 inches wide and 2 inches tall.

Another view...
Yet another view...
And here is a comparison between the Cake Topper prototype and my previous prototype of a one-quarter sized basset -- makes for a good contrast, particularly since his coloring is blue, rather than brown. :)
There are still some coloring issues to work out (some bricks I didn't have enough in the right colors I was looking for, and if you want me to try to match your fiance's basset, I can try for that as well).
Anyhow, this should give you a basic idea of size/look, to make sure we're headed in the right direction.